Dismissal triggers when you take a small amount of damage, and reduces that damage by up to half. Since it only triggers on small amounts of damage, you'd therefore expect it to be checked after other forms of damage reduction, so that it would have a higher chance of activating. Instead, it triggers before Resonance Shield, creating anti-synergy. Here's a screenshot of the combat log to demonstrate. In the spot I've underlined, Antimagic Shield triggers, then Dismissal cuts the remaining damage in half, then Resonance Shield triggers after, cutting the damage in half again. Resonance should trigger before Dismissal.

Dismissal is worthless if it doesn't synergize with other forms of damage reduction, which is why I'm reporting this as a bug.